And what exactly would that have accomplished? Allah is the one who guides people to the truth and He is always present: the prophets and messengers are just tools He uses to relay His message. No matter the time period or location, the vast majority of people who have ever been alive still won't have been present to witness it, and the disbelievers are still going to find reasons to disbelieve.
This is just the sort of argument made by people who choose to put their faith into camera phones and Google searches rather than into Allah. People throughout history never needed such things in order to believe, what makes today's people any different?
109 And they swear by Allah their strongest oaths that if a sign came to them, they would surely believe in it. Say, "The signs are only with Allah ." And what will make you perceive that even if a sign came, they would not believe.
110 And We will turn away their hearts and their eyes just as they refused to believe in it the first time. And We will leave them in their transgression, wandering blindly.
111 And even if We had sent down to them the angels [with the message] and the dead spoke to them [of it] and We gathered together every [created] thing in front of them, they would not believe unless Allah should will. But most of them, [of that], are ignorant.
— Al-'An'am 109-111